Computer processors sometimes have adjustable operating parameters, such as the processor's operating voltage or the processor's clock frequency. In some laptop computer systems, for example, it may be desirable to reduce the processor's operating voltage and/or the processor's clock frequency in order to save power. The operating point (i.e., the level at which the processor operates) for such adjustable parameters may be changed during processor operation or at processor boot-up time, such as at a cold start or a reset. Adjustable operating parameters may be programmed to settings that are referenced by, for example, a set of operating points provided by the processor manufacturer. Such a processor operating parameters may be said to be adjustable or dynamic even though there may only be limited levels of adjustment, limited times when adjustments are made, and/or limits on the devices and mechanisms that cause the adjustment.
As noted above, one example of an adjustable operating parameter may be a processor's operating voltage. In some processors the processor's operating voltage is governed by an external voltage regulator, in which case the voltage regulator may accept a voltage select input that defines a desired voltage to be provided to the processor. The voltage regulator's voltage select input may be provided by the processor itself or a chipset and may be programmable by external software. Another example of an adjustable operating parameter may be processor clock frequency. Adjustable processor clock frequency may be supported, for example, by programmability of a divider between an external input source clock (e.g., an external bus clock) and an internal processor core clock. The processor core clock may represent some integer of a fractional multiple of the external clock, such as generated by a phase-lock-loop (PLL) or equivalent function. In this case, the internal processor clock operating frequency may be changed by reprogramming the value of the external-bus-to-core-clock divider.
Computer security involves techniques and mechanisms for protecting a computer or computer system from compromise through unauthorized access. Such security techniques may involve software and/or hardware security mechanisms and may include techniques directed to the security of the processor.